Clear Cell Sarcoma of the Kidney: A case in 39 year old man

Yoo, Hyun Ju; Kang, Yun Kyung; Joo, Mee; Lee, Hye Kyung; Kim, Dae Woo; Park, Suk San

Abstract

Clear cell sarcoma of kidney(CCSK) is a rare pediatric neoplasm characterized by a predominating component of clear cells, a predilection for metastases to bone, and a poor prognosis. The incidence of CCSK peaks during the 2nd year of life and adult cases are very rare. We report a case of CCSK encountered in the right kidney of a 39-year-old man. Grossly, it was a lobulated mass showing infiltrative margin, measured 7x5.5x5cm and had a homogeneous gray-tan color with a soft, fish-flesh consistency. Microscopically, about half of the tumor revealed the classic pattern of CCSK, having tumor cell cords or nests separated by the characteristic alveolar capillary networks. The tumor cells had clear pale cytoplasm, bland looking round nuclei and inconspicuous nucleoli. The other half showed the epithelioid-trabecular pattern forming pseudorosette or cord-like structures. Immunohistochemically, there was only a focal positive reaction to vimentin. Ultrastructurally, the tumor cells showed the primitive nephrogenic mesenchymal differentiation such as electron lucent cytoplasm, a small amount of organelles, scanty heterochromatin, inconspicuous nucleoli, and a lack of flocculant basal lamina material around the cytoplasmic membrane. We consider that this is a case of CCSK occuring in the oldest patient ever reported, confirmed by both immunohistochemistry and electron microscopy.